Camptothecins, platinum-type anticancer compounds such as cisplatin, and anticancer compounds such as taxanes are active against a wide variety of tumor cells, and are expected as therapeutic agents such as anticancer agents (Patent Documents 1 and 2). Some of these compounds are excellent anticancer agents, but there is a demand for further activity improvement.
Many of these compounds are lipophilic, and because of their low water solubility, their use in injections (parenteral administration) is sometimes limited (Patent Document 1). Water-soluble prodrugs have been studied in an attempt to solubilize such lipophilic pharmaceutical agents in water (Non-Patent document 1 and Patent Document 1).    [Patent Document 1] WO 03/043631    [Patent Document 2] WO 03/045952    [Non-Patent Document 1] Shan et al., J. Pharm. Sci., 86(7), 765-767, 1997